Semeru's eruptive history is extensive. Since 1818, at least 61 eruptive periods have been recorded (11 of which resulted in fatalities) consisting of lava and
pyroclastic flows. Almost all historical eruptions have had a
Volcanic Explosivity Index (VEI) of 2 or 3. Semeru has been in a state of near-constant eruption from 1967 to the present. The volcano's most recent eruption occurred in 2025.
2021 eruption In 2021, Semeru erupted in January, and on 4 and 6 December. The eruption caused high ejections, lava flows for and ash rains for . At least 57 people died, 104 more were injured, while 23 were unaccounted for. More than 10,000 people were displaced, and 1,027 houses, 43 public facilities and two bridges affected. that reached , along with an ash cloud that reached a height of . As of 20 November 2025, three people were injured, 1,156 were displaced, and 200 houses along with one school building were damaged. ==Legends==